The present invention relates in general to piezoelectric-type portable propane gas hand torches, and more particularly to such piezoelectric igniter-type gas hand torches having finger actuated mechanical structure for activating the piezoelectric spark-producing device solely responsive to mechanical hand pressure and valving the gas to flow into the burner tube immediately prior to spark generation to insure proper ignition.
Piezoelectric spark-producing devices for use in igniting combustible fuels such as propane gas and similar fuels which can be stored in portable containers have been known for a number of years. Such devices typically have a hammer which is moved into force impact with an anvil structure of a piezoelectric crystal assembly forming part of an electrical circuit having a spark gap. When the crystal is deformed by the hammer blow, a voltage is generated in the circuit of sufficient magnitude to create a spark in the gap area of the circuit. Typical of such piezoelectric spark-producing devices are those shown in prior U.S. Pat. Nos. 3,509,388 dated Apr. 28, 1970 and 4,139,792 dated Feb. 13, 1979, both assigned to Matsushita Electric Industrial Co., Ltd. In those devices, the hammer is actuated by moving a slidable finger-piece or plunger slidably supported in telescoping relation projecting into the outer housing, which during an initial portion of its inward stroke arms a spring while restraining the hammer against movement towards the crystal, and then suddenly releases the hammer to be driven by the spring into spark generating impact with the crystal stack. Other mechanical arrangements have also been devised in prior art piezoelectric-type spark-producing devices for driving the hammer into spark generating impact with the crystal structure.
Other similar devices have been proposed, as U.S. Pat. No. 3,802,828 granted Apr. 9, 1974 to Mercer et al, wherein the hammer is driven by a piston which responds to fluid pressure from the combustible fuel source, in a manner which ensures that the gaseous fuel has reached the combustion chamber portion of the burner by the time the hammer is allowed to impact against the crystal and produce the spark for igniting the fuel in the burner.
An object of the present invention is the provision of a novel portable finger-activated gas hand torch with a piezoelectric igniter, wherein the igniter is associated with a finger-operated control knob in a novel manner facilitating manufacure and reliable operation of the torch, and which provides improved safety features insuring igniting of the gaseous fuel from the attached container and operation only while safely in the hands of the user maintaining the control knob in depressed condition by finger-pressure, thus ensuring automatic extinguishing of the torch if it is dropped or finger-pressure is released from the control knob for any reason.
Another object of the present invention is the provision of a novel portable gas hand torch of the piezoelectric igniter-type, as described in the immediately preceding paragraph, wherein the action of the igniter and the valve controlling release of gaseous fuel to the combustion chamber of the burner tube reliably operate in a manner such that gaseous fuel reaches the combustion zone of the burner tube immediately prior to spark generation.
Yet another object of the present invention is the provision of a novel portable gas hand torch of the piezoelectric igniter-type, constructed in such manner that the torch may be used upside down or in any position without flare-out of flame or significant changes in flame pattern and wherein the control knob which in its ON position must be maintained depressed to continue the burning condition the burning condition is spring biased to cause shut off of gas fuel supply so that the torch will not be accidentally maintained in burning condition when accidentally overturned or rolling on surfaces onto which it may be dropped.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.